This is a testharness.js-based test.
[FAIL] Custom properties are not allowed in the outer scope of @keyframes rules
assert_equals: expected "@keyframes foo {\\n 0% { --valid-var: 4; }\\n 100% { left: 10px; }\\n}" but got "@keyframes foo { \\n 100% { left: 10px; }\\n}"
Harness: the test ran to completion.